Gravel / Gravé / Gnarmac / Groad / ATB

I still don't fully understand capacity. It implies you're going to cross chain big-big and small-small, right? What if you just don't do that, and shift your chainring at the 'right' time? Then you can get away with a lot more (range)?

I guess the downside is you have shift your chainring at the right time, otherwise you're screwed.

You could have a chain shorter than recommended, and never use big-big or even big-slightly-big. The trouble with that is that if you accidentally go into too big a cog at the back, the whole drivetrain locks solid and you have to dissassemble your bike to undo the unholy mess. Not recommended.

If you set your chain length to permit (just) big-big combo for those moments of foregetfulness then if you exceed the RD's capacity on small-small then the cage will rotate backwards so far the chain will rub on itself as it goes past the upper jockey wheel and on its way from the lower jockey wheel to the chainring. Sounds unpleasant, but not the end of the world. Changing into the big ring at the front or a bigger cog at the back solves the issue easily.